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Makes the speech/music probability estimation mode conservative

This is done using an adaptive beta and an estimate of the speech
and music detection confidence

--- a/src/analysis.c

+++ b/src/analysis.c

@@ -180,6 +180,7 @@

       psum += tonal->pmusic[i];

    for (;i<DETECT_SIZE;i++)

       psum += tonal->pspeech[i];

+   psum = psum*tonal->music_confidence + (1-psum)*tonal->speech_confidence;

    /*printf("%f %f\n", psum, info_out->music_prob);*/

    info_out->music_prob = psum;

@@ -479,19 +480,22 @@

     {

        float tau, beta;

        float p0, p1;

-       float max_certainty;

        /* One transition every 3 minutes */

        tau = .00005f*frame_probs[1];

        beta = .05f;

-       max_certainty = .01f+1.f/(20.f+.5f*tonal->last_transition);

-       max_certainty = 0;

+       if (1) {

+          /* Adapt beta based on how "unexpected" the new prob is */

+          float p, q;

+          p = MAX16(.05f,MIN16(.95f,frame_probs[0]));

+          q = MAX16(.05f,MIN16(.95f,tonal->music_prob));

+          beta = .01+.05*ABS16(p-q)/(p*(1-q)+q*(1-p));

+       }

        p0 = (1-tonal->music_prob)*(1-tau) +    tonal->music_prob *tau;

        p1 =    tonal->music_prob *(1-tau) + (1-tonal->music_prob)*tau;

        p0 *= (float)pow(1-frame_probs[0], beta);

        p1 *= (float)pow(frame_probs[0], beta);

-       tonal->music_prob = MAX16(max_certainty, MIN16(1-max_certainty, p1/(p0+p1)));

+       tonal->music_prob = p1/(p0+p1);

        info->music_prob = tonal->music_prob;

-       info->music_prob = frame_probs[0];

        float psum=1e-20;

        float speech0 = (float)pow(1-frame_probs[0], beta);

@@ -526,7 +530,30 @@

        for (i=1;i<DETECT_SIZE;i++)

           psum += tonal->pspeech[i];

-       /*printf("%f\n", psum);*/

+       /* Estimate our confidence in the speech/music decisions */

+       if (frame_probs[1]>.75)

+       {

+          if (tonal->music_prob>.9)

+          {

+             float adapt;

+             adapt = 1.f/(++tonal->music_confidence_count);

+             tonal->music_confidence_count = IMIN(tonal->music_confidence_count, 500);

+             tonal->music_confidence += adapt*MAX16(-.2f,frame_probs[0]-tonal->music_confidence);

+          }

+          if (tonal->music_prob<.1)

+          {

+             float adapt;

+             adapt = 1.f/(++tonal->speech_confidence_count);

+             tonal->speech_confidence_count = IMIN(tonal->speech_confidence_count, 500);

+             tonal->speech_confidence += adapt*MIN16(.2f,frame_probs[0]-tonal->speech_confidence);

+          }

+       } else {

+          if (tonal->music_confidence_count==0)

+             tonal->music_confidence = .9;

+          if (tonal->speech_confidence_count==0)

+             tonal->speech_confidence = .1;

+       }

+       psum = MAX16(tonal->speech_confidence, MIN16(tonal->music_confidence, psum));

     }

     if (tonal->last_music != (tonal->music_prob>.5f))

        tonal->last_transition=0;

--- a/src/analysis.h

+++ b/src/analysis.h

@@ -65,6 +65,10 @@

    int analysis_offset;

    float pspeech[DETECT_SIZE];

    float pmusic[DETECT_SIZE];

+   float speech_confidence;

+   float music_confidence;

+   int speech_confidence_count;

+   int music_confidence_count;

    int write_pos;

    int read_pos;

    int read_subframe;